Canada needs the capability for early detection, understanding and action to address One Health threats and reduce their potential wide-reaching impact. To fill this need, the Public Health Agency of Canada, in collaboration with partners across sectors, developed a protocol for a One Health Approach to Risk Assessment (OHARA). The goal of this protocol is to unify efforts for multi-sector risk assessments on One Health hazards. The protocol was developed using extensive consultation with Federal-Provincial-Territorial departments and agencies for public health, agriculture, and the environment from August 2022 to November 2023. The development of the OHARA protocol brought together risk assessors from multiple sectors to understand roles and responsibilities, establish core principles, share methodologies, and strengthen networks.